The present invention relates to a reflection multiplier radio wave marker system which employs a radio wave lane marker installed in the surface of a road for providing a vehicle with information about location in the width direction in a traffic lane and road status, and to a traffic system.
FIG. 6 shows a conventional radio wave marker system. In FIG. 6, a reflection multiplier radio wave marker (hereinafter referred to as marker) 54 is installed in the surface of a road, while a marker sensor 60, which is formed of a transmit antenna 55, a receive antenna 56 and a detectionxe2x80xa2processing portion 57, is mounted on board a vehicle.
The transmit antenna 55 transmits electric wave to a marker 54, the electric wave reflected by the marker 54 is received by the receive antenna 56. The detectionxe2x80xa2processing portion 57 processes the signal received to calculate location of the vehicle in relation to the marker 54.
Referring to FIG. 6, one unit of transmit antenna 55 is disposed substantially in the middle; while the receive antenna 56 is disposed for three units, in the left, in substantially the middle and in the right.
Intensity of the electric wave reflected by a marker 54 is higher when the marker 54 is located closer to the transmit antenna 55 of marker sensor 60. Receiving sensitivity at a receive antenna 56 of marker sensor 60 goes higher when it is located closer to marker 54.
When distance between a marker 54 and a transmit antenna 55, or a receive antenna 56, of marker sensor 60 exceeds beyond a certain range, the marker sensor 60 becomes unable to detect the marker 54.
Being dependent on the shape and size of a transmit antenna 55 mounted at the front of a vehicle, it is difficult for a conventional radio wave marker system to detect location of a vehicle in relation to a marker 54 in the direction of width covering the entire range of a vehicle width. Namely, if a single transmit antenna 55 is to cover the entire range of a vehicle width evenly, it should be a loop antenna whose size is identical substantially to the vehicle width. In practice, such a loop antenna poses a great restriction in mounting it on board a vehicle.
In order to enable a vehicle to detect the location in relation to a marker in substantially the entire range of the vehicle width using a means mounted at the vehicle front, the transmit antenna 55 needs to be made compact in size and high in sensitivity. These are not easy tasks to achieve.
A reflection multiplier radio wave marker system which comprises a plurality of transmit antennas mounted on board a vehicle for transmitting electric wave signals in a first frequency; a reflection multiplier radio wave marker installed in the surface of a road, which reflects and transmits the electric wave signal of first frequency after multiplying it into an electric wave of a second frequency; and a receive antenna mounted on board the vehicle for receiving the electric wave of second frequency. The system detects location of the vehicle in a traffic lane based on the second frequency electric wave signal reached from a marker. Range of the location detection is extending to cover substantially the entire width of the vehicle.